(1) Field of the Invention
The present invention relates to a light amplifier formed of a semiconductor material provided with the faculty of light amplification based on the magnetoelectric-photo effect, particularly, at the room temperature, as well as over a wide range of wavelength at low temperatures such as liquid helium temperature.
(2) Description of the Prior Art
As for the conventional solid-state light amplifier, a light amplifier according to the principle that the light amplification is effected by the stimulated emission from the activated amplifying medium, such as a light amplifier consisting of a semiconductor material in which a population inversion region of electrons and holes is formed on the basis of light pumping effected by a gas laser, a solid-state laser and the like, and a light amplifier consisting of a p-n junction semiconductor material having a population inversion region of electrons and holes in the central portion of the junction region applied with the foward current, has been employed.
It is required for the conventional light amplifier according to the above mentioned principle of light amplification to miniaturize the device, as well as to improve the efficiency of light amplification on the application thereof to the infrared radiation equipment for the optical communication use and for the military industry use.
However, for instance, in the conventional p-n junction type semiconductor laser diode, the width of active region is restricted so narrow as the diffusion length of the carrier, for instance, in the order of 10 .mu.m. That is, in a p-n junction type laser diode as shown in FIG. 1, a p-n junction region 3 arranged between an n-type semiconductor substrate 1 and a p-type semiconductor layer 2 is applied with a bias voltage through lead wires 6 and 7, and, in this situation, an input light through an end surface 4 polished into a mirror surface is intensified and taken out of an opposite surface 5 as a laser beam 8. However, the width of the p-n junctions 3 appearing on the input surface 4 is extremely narrow as mentioned above, so that it is very difficult to get the input light coupled with the extremely narrow end surface of the p-n junction region 3. In addition, it is required for the operation in the infrared range to refrigerate the device down to the liquid nitrogen temperature, that is, 77.degree. K. or to temperature lower than 77.degree. K., because of the difficulty in forming the effective p-n junction for narrow-gap semiconductors, such as InSb, Hg.sub.1-x Cd.sub.x Te and Pb.sub.1-x Sn.sub. x Te.
In short, the conventional semiconductor light amplifier utilizing p-n junction has the serious defect of inconvenience in practical use. As stated earlier with respect to lasers with p-n junctions, it should be noted that the inverted population of electrons and holes needed for lasing of the laser diode is caused by the injection of excess carriers through the p-n junction and hence by the forward current passing through the junction.
In short, the conventional semiconductor light amplifier has the serious defect of inconvenience in practical use.